SMALL PIN (.154 A~) - If your AR rifle is NOT a Colt or your Colt was produced before 1991 or after 2009 it will take a SMALL PIN CMC's innovative, self-contained and easy-to-install AR-15 trigger groups, have been completely re-tooled to maximize production capacities, incorporate new design enhancements and reduce cost. CMC's AR-15 trigger groups have always yielded exceptional trigger pull dynamics for our tens of thousands of satisfied customers. However, keeping up with high demand has been difficult since the introduction. CMC is confident the new production tooling and setup, incorporating the most advanced methods available, will not only yield the highest quality but will also keep the supply lines full so every AR-15 shooter who places the highest demands on quality, function, and reliability, will no longer have extensive lead times for obtaining these innovative trigger groups. And thanks to our multi-patented designs, a fine match grade trigger pull is now an extremely simple upgrade to implement. Install the fully self-contained, ready-to-go trigger group, safety check, and it's done. *DO NOT OVER TIGHTEN!! FEATURES 2 posts, 4 Screws, 2 wrenches Positive retention of trigger assembly Assembly tools provided with kit Easy to install or remove Improved reliability of trigger assembly No sharp protrusions to interfere with hand or glove